Gas-filled discharge path in a form of a spark gap or an overvoltage diverter

ABSTRACT

In order to optimize the so-called light-dark effect, i.e., the difference in ignition voltage between the first and second ignition after dark storage in gas-filled discharge paths, an additional component made of an oxide compound of cesium and a transition metal such as tungsten, chromium, niobium, vanadium or molybdenum is added in a quantity of 5 to 25% by weight to the activating compound which is comprised of several components. The other components of the activating compound include a barium compound and a transition metal in metallic form such as titanium, and an alkaline halide or an alkaline earth halide and/or sodium silicate and/or potassium silicate as a basic component.

FIELD OF THE INVENTION

The invention is in the field of electronic components and is theconstruction of gas-filled discharge paths having at least twoelectrodes in which an electrode activation compound having severalcomponents is applied to at least one of the electrodes in order toensure their ignition properties.

BACKGROUND INFORMATION

In order to ensure the particularly desired performance characteristicsuch as igniting voltage, response time, static response voltage anddynamic response voltage, extinction voltage and glow operating voltagein discharge paths such as ignition gaps or overvoltage diverters filledwith inert gas, various measures such as the structural design of theelectrodes, the type and pressure of the gas filling and the selectionof the activation compound applied to the active surfaces of theelectrodes must be adjusted to one another. To produce definitiveignition conditions, it is also customary in this connection to arrangeone or several ignition strips on the inside wall of the glass orceramic insulator and a special ionization source may be provided, ifnecessary. Thus, for instance, a conventional overvoltage diverter hastwo electrodes inserted into the front ends of a ceramic insulator, theelectrode surfaces facing each other being coated with an activationcompound, the latter being arranged in depressions in the electrodesurface. Several ignition strips extending in the axial direction of theceramic insulator are arranged on the inside wall, the ignition stripsbeing designed as middle ignition strips without a direct connection tothe electrodes (see U.S. Pat. No. 4,266,260 corresponding to GermanPatent No. 28 28 650 C2). It is more customary to apply an additionalionization source in the form of a punctiform deposit of a radioactivematerial on the inside wall of the insulator in gas-filled overvoltagediverters which are located in a space sealed off against the ionizationsource in the form of a punctiform deposit of a radioactive material onthe inside wall of the insulator in gas-filled overvoltage diverterswhich are located in a space sealed off against the effect of externallight during their operation. Alternatively, the gas filling of theovervoltage diverter may include a radioactive gas (see U.S. Pat. No.3,755,715). In order to ensure a very low ignition delay in gas-filledovervoltage diverters in the dark space, the use of anelectroluminescent material as an additional ionization source is alsoknown, the electroluminescent material being applied to the inside wallof the insulator as a coating connecting the two electrodes of thediverter (see German Patent No. 43 18 944 C2).

SUMMARY OF THE INVENTION

An object of the present invention is to provide a gas-filled dischargepath (such as a spark gap or an overvoltage diverter) with at least twoelectrodes so that the gas-filled discharge path has a very low ignitiondelay in the dark space even without the use of an additional ionizationsource.

In order to attain this objective, according to the invention anelectrode activation compound made up of several components is appliedto at least one of the electrodes of the diverter, the electrodeactivation compound containing in addition to the customary basiccomponents in the form of one or several alkaline halides or alkalineearth halides and/or sodium silicate and/or potassium silicate in anamount of 30-60% by weight, as further components a barium compound anda so-called transition metal in metallic form such as titanium, hafnium,zirconium, vanadium, niobium or chromium in a quantity of 5 to 25% byweight each and an oxide compound of cesium and a so-called transitionmetal such as tungsten, chromium, molybdenum, niobium or vanadium, i.e.,cesium wolframate (Cs₂ WO₄), cesium chromate (Cs₂ Cr₂ O₇), cesiummolybdate (Cs₂ MoO₄), cesium niobate (CsNbO₃) or cesium vanadate (Cs₂VO₃) also in an amount of approximately 5 to 25% by weight.

When an activation compound composed according to the present inventionis used, it has been shown that the ignition voltage of the firstignition after the discharge path has been stored for 24 hours indarkness is within the range required by the users of discharge paths ofthis type, particularly not deviating more than 10 to 15% from theignition voltage value of the second ignition. Beyond that, the use ofcesium wolframate or one of the other cesium compounds provided inconnection with the present invention as additional components of anactivation compound ensures very good extinction characteristics of thedischarge path and stable electrical properties even after extendedstorage in darkness and after having been supplied with electric power.In particular, these electrical properties are the nominal dischargecurrent, the nominal discharge alternating current and the service lifeload.

A benefit obtained using the present invention is made evident by thefact that a barium compound, preferably a barium-aluminum alloy (BaAl₄),and a transition metal in metallic form such as titanium, hafnium,zirconium, vanadium, niobium or chromium are among the components of theelectrode activation compound. In this connection, the use ofbarium-aluminum and metallic titanium as components of an activationcompound is described in German Patent No. 26 19 866 as is the use ofthe basic component in the form of one or several alkaline halides oralkaline earth halides and/or sodium silicate and/or potassium silicate(see German Patent Nos. 26 19 866 C2, 37 23 571 C2, 27 35 865 C2).Furthermore, the use of an oxide compound of cesium and a transitionmetal such as zirconium, tungsten, tantalum and molybdenum as emissionmaterials for discharge lamps in order to make a low breakdown voltageand operating voltage possible during the total service life of the lampis known. In this connection the oxide compound is dispersed in thepores of a sintered compact made of high-melting metal. Barium aluminateor barium wolframate may be used as additional emission material (seeGerman Patent No. 30 08 518 C2).

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a gas-filled overvoltage diverter according to FIG. 1 ofGerman Patent No. 43 18 994 C2.

DETAILED DESCRIPTION OF THE INVENTION

In a gas-filled overvoltage diverter, which according to FIG. 1 ofGerman Patent No. 43 18 994 C2 is made up of a ceramic insulator 3 andtwo electrodes (12) inserted into the front end, an activation compound4 has been incorporated into the waffled surface of the electrodes, theactivation compound containing as a basic component potassium chloridein an amount of 50% by weight, metallic titanium in an amount of 17% byweight, a barium-aluminum compound also in an amount of 17%. by weightand cesium wolframate in an amount of 16% by weight. Furthermore theactivation compound may contain smaller proportions of oxides of cesiumand the transition metals used, i.e., cesium oxide, titanium oxide andtungsten oxide.

What is claimed is:
 1. A gas-filled discharge arrangement, comprising:atleast two electrodes; and an electrode activation compound having aplurality of components applied to at least one of the at least twoelectrodes, the electrode activation compound including, a basecomponent, at least one of an alkaline halide, an alkaline earth halide,a sodium silicate, and a potassium silicate, in a first amount ofapproximately 30% to 60% by weight, the electrode activation compoundfurther including a barium compound and a first transition metal in asecond amount of 5% to 25% by weight, the first transition metal beingin metallic form, and the electrode activation compound furtherincluding an oxide compound, the oxide compound including cesium and asecond transition metal in a third amount of approximately 5% to 25% byweight.
 2. The gas-filled discharge arrangement according to claim 1,wherein the gas-filled discharge arrangement includes one of a spark gapand an overvoltage diverter.
 3. The gas-filled discharge arrangementaccording to claim 1, wherein the first transition metal includes one oftitanium, hafnium, zirconium, vanadium, niobium and chromium.
 4. Thegas-filled discharge arrangement according to claim 1, wherein thesecond transition metal includes one of tungsten, chromium, molybdenum,niobium and vanadium.
 5. The gas-filled discharge arrangement accordingto claim 1, wherein the oxide compound includes one of cesium wolframate(Cs₂ WO₄), cesium chromate, cesium molybdate (Cs₂ MoO₄), cesium niobateand cesium vanadate (CS₂ VO₃).
 6. The gas-filled discharge arrangementaccording to claim 5, wherein the cesium chromate includes one of Cs₂Cr₂ O₇, and Cs₂ CrO₄.
 7. A gas-filled discharge arrangement,comprising:an overvoltage diverter, including:at least two electrodes;and an electrode activation compound having a plurality of componentsapplied to at least one of the at least two electrodes, the electrodeactivation compound including, a base component, at least one of analkaline halide, an alkaline earth halide, a sodium silicate, and apotassium silicate, in a first amount of approximately 30% to 60% byweight, the electrode activation compound further including a bariumcompound and a first transition metal in a second amount of 5% to 25% byweight, the first transition metal being in metallic form, and theelectrode activation compound further including an oxide compound, theoxide compound including cesium and a second transition metal in a thirdamount of approximately 5% to 25% by weight.
 8. The gas-filled dischargearrangement according to claim 7, wherein the oxide compound includesone of cesium wolframate (Cs₂ WO₄), cesium chromate, cesium molybdate(Cs₂ MoO₄), cesium niobate and cesium vanadate (Cs₂ VO₃).
 9. Thegas-filled discharge arrangement according to claim 8, wherein thecesium chromate includes one of Cs₂ Cr₂ O₇, and Cs₂ CrO₄.